TEENAGERS who use cannabis delay the development of their brain, says a study.

It also found dope use among adolescents had a “more pronounced and lasting” negative effect on the brain than alcohol.

The study, published in the American Journal of Psychiatry, examined the relationship between alcohol, cannabis use and cognitive development among Canadian adolescents.

Dr Patricia Conrod, of the Universite de Montreal, said: “The message to young people who wish to succeed in school and their adult life is that they should do what they can to delay their cannabis use as much as possible.

“A regular cannabis user in the 10th grade was three years behind their peers in their development of inhibitory control and equivalent to their non-cannabis using peers in the seventh grade.”

Researchers from CHU Sainte-Justine and Universite de Montreal in Canada carried out the research over a period of four years, studying 3,800 adolescent subjects.